Walking burns like, what, 5 kcal/minute (generous)? If non-Americans walk on average 20 more minutes a day (generous), that's like 100 kcal per day. Or about 7kg at 15 kcal/kg basal metabolic rate, not taking into account for increased appetite.
While you have a good point, I want to nitpick a little:
As an American who recently moved to Europe, I don't think 20 minutes of walking per day is being generous. COVID-related measures aside, I find I add about 20min/day of walking easily, and more if I need to do something (e.g. buying groceries). Now, in the US I own a car and here I do not -- but in my Midwestern town I am totally obligated to own and operate a car. Here in Europe I get along fine with walking, riding a bike, and using public transport.
